Finding information about a trigger path

Overview

Teaching: 10 min
Exercises: 10 min

Questions

Objectives

• Learn different ways to look up information about a trigger path

Prerequisites

Set up your machine following instructions in setup first.

Find the L1 seed of the MET HLT path

There are different ways to learn which is the L1 seed of a specific HLT path. Two examples will be tested in this exercise:

• looking into OMS;
• looking into web-based confdb;
• inspecting a HLT configuration.

In the context of this exercise, we will retrieve the information of the HLT_PFMET170_HBHECleaned_v* path from OMS for a specific run (run 284043) and HLT configuration (/cdaq/physics/Run2016/25ns15e33/v4.2.3/HLT/V2).

OMS method

As a first step, connect to OMS

• Click on "Runs > Triggers > HLT Path Report",
• Use search option at the bottom left (“FILTER > Path Name”) to look for HLT_PFMET170_HBHECleaned_v*.
• Find the information about the L1 seed names of the HLT path of interest.

Then move to the L1 Trigger rate page in OMS and search for the L1 seeds there to have a look at the rates and prescales of these L1 seeds.
(Note that you might need to increase the number of rows at the bottom of the page to find them.)

Web-based confdb

The web-based confdb is a web-based GUI of the database that holds all of CMS HLT configurations.
One can inspect any given HLT menu without downloading one or connecting to the database.
More information about the web-based confdb can be found in these slides.

Let’s try to find the /cdaq/physics/Run2016/25ns15e33/v4.2.3/HLT/V2 menu in the GUI.

• Connect to https://hlt-config-editor-confdbv3.app.cern.ch/
• Click “Configurations > Open remote”
• In the drop-down menu, select online
• Follow the directory of the menu /cdaq/physics/Run2016/25ns15e33/v4.2.3/
• Select “V2” from the side penal, and click “OK”

After retriving from the DB, you can see all the paths.

• Type the name of the path HLT_PFMET170_HBHECleaned into the search box in the left panel
• Expand the path. This shows all the modules that the HLT path will run in sequence.
• The L1 seed of a HLT path is always the first module (after the HLTBeginSequence) starting with the name hltL1sXXXX
• Click on hltL1sETM50ToETM120
• In the right panel, the L1SeedsLogicalExpression shows the L1 seeds used by the path.

Checklist

You should see the same L1 seeds that you find from OMS.

Inspecting a HLT configuration

hltGetConfiguration is the official command to retrive a HLT configuration from the database.

Caution

Since hltGetConfiguration involves connecting to the confdb database directly, this command should never be used in a large number of jobs or programatic loop. It should only be used interactively.

ssh -f -N -D 1080 <yourUserName>@lxplus.cern.ch 
hltConfigFromDB --configName --adg /cdaq/physics/Run2016/25ns15e33/v4.2.3/HLT/V2 --dbproxy --dbproxyhost localhost --dbproxyport 1080 > dump_hlt_online_2016G.py

If you have connection issue, simply inspect one that has been downloaded for you

xrdcp root://cmseos.fnal.gov//store/user/cmsdas/2023/short_exercises/Trigger/dump_hlt_online_2016G.py .

Then, inspect the HLT configuration dump_hlt_online_2016G.py to look for the information about the L1 seed of the path into it:

grep 'process.HLT_PFMET170_HBHECleaned_v9' dump_hlt_online_2016G.py

You should see the expected output below:

process.HLT_PFMET170_HBHECleaned_v9 = cms.Path(process.HLTBeginSequence+process.hltL1sETM50ToETM120+process.hltPrePFMET170HBHECleaned+process.HLTRecoMETSequence+process.hltMET90+process.HLTHBHENoiseCleanerSequence+process.hltMetClean+process.hltMETClean80+process.HLTAK4PFJetsSequence+process.hltPFMETProducer+process.hltPFMET170+process.HLTEndSequence)

Questions

To conclude, answer the following questions:

• Which was the lowest threshold L1 seed active in the L1 menu?
• Which is the lowest threshold L1 seed unprescaled?
• How is it called the HLT module that contains the information about the L1 seeding?

Key Points